1. Field of the Invention
The present invention relates to the art of spreading sealant onto a paved surface, such as a blacktop driveway.
2. The Prior Art
A variety of machines have in the past been proposed for the spreading of materials for sealing or otherwise improving the surface quality of pavement. For example, U.S. Pat. No. 791,726 discloses an apparatus for spreading bitumen and the like. This apparatus consists primarily of a tank with a central opening at the lower portion for dispensing the bituminous material, and having a curved, flexible spreader located beneath the tank. Wheels are mounted behind the tank for easy transportation of the apparatus when not in use. This design has a number of serious drawbacks. First, the bitumen is dispensed from the tank only in the central area. This, of course, will cause uneven distribution of the material across the width of the spreader's path since none of the materials is dispensed at the outboard regions of each swath. A second disadvantage is that the curved spreader will tend to further concentrate the material on the pavement in the center of each swath as the operator pulls the apparatus along. Third, the device is difficult to pull along since it rests on the wheels only when not in use. Fourth, the apparatus has no adjustable stop or other means for limiting the flow rate to a predetermined amount on successive passes over the surface. Each time the valve is closed, the operator must estimate the proper valve position upon reopening. In addition to the above, this design provides only for a squeegee effect which levels off the material deposited on the surface to be coated, without providing a means for forcing the coating material into the gaps and pores of the surface.
U.S. Pat. No. 1,419,537 embodies features which represent some improvement over prior designs, such as the addition of a rigidly mounted brush and of wheels which support the weight of the tank. However, there are disadvantages to this design as well. For example, the brush and wiper members are rigidly mounted on the tank and do not independently ride up and down to provide for even spreading over uneven surfaces. The wheels are arranged so that, when not in use, the operator must lift the majority of the device's weight to transport it without having the brush and wiper dragging over the surface. The arrangement also requires the operator to push, rather than pull the device; this means he must necessarily walk on the viscous material just deposited. Furthermore, the valve system is located so high in the flow path that the operator must anticipate the amount of material flowing onto the surface after the valve is closed. Failure to accurately estimate this amount will cause too much or too little coating to be deposited at the end of a swath.
U.S. Pat. No. 821,152 discloses an oil sprinkling device which, while dispensing oil across the width of a swath, provides no means for brushing the material into the surface or scraping it off level with the surface. In addition, having the valves so far from the sprinkler causes a good deal of the oil to be wasted when the flow is shut off at the end of a swath.
To concrete distributing cart described in U.S. Pat. 1,641,703 has several of the disadvantages noted above, the major one of which is that no means for brushing the material into the interstices of the surface to be filled is provided.
The Stone Spreader of U.S. Pat. No. 1,811,324 employs an auger device for distribution of the material, but is not adapted for spreading a wide path of viscous material.